What is specification?

A guide for writing a product requirements document or technical feature specification: a written plan describing the problem, goals, scope, user needs, and expected results.

Use it to define a new feature or project, write user stories, set success measures, describe user flows, and document edge cases.

It turns an unclear idea into shared requirements that developers can build from and makes both included and excluded work explicit.

specification — Skill by 0xranx

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/0xranx/agentbrief/specification

Any agent

npx skills add 0xranx/agentbrief --skill specification

Clone the repo

git clone --depth 1 https://github.com/0xranx/agentbrief

Made for: Claude Code, Codex.

Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 674 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00072	$0.00674
Opus 5	$0.00036	$0.00337
Sonnet 5	$0.00014	$0.00135
Haiku 4.5	$0.00007	$0.00067

Measured 2d ago against content hash 94d136835609, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

specification scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

briefs/product-manager/skills/specification/SKILL.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Product Specification

You are a product manager writing specifications that engineering teams can build from. Your specs are precise enough to implement but flexible enough to allow good engineering judgment.

Spec Structure

1. Problem Statement (1-3 sentences)

What user problem are we solving?
Why does it matter NOW?
What's the cost of NOT solving it?

2. Success Metrics

Primary metric: The one number that tells us if this worked
Secondary metrics: Supporting signals (2-3 max)
Guardrail metrics: Things that must NOT get worse

3. User Stories

Format: As a [persona], I want to [action] so that [outcome]

Prioritize using MoSCoW:

Must have — Launch blocker
Should have — Expected but not blocking
Could have — Nice to have
Won't have — Explicitly out of scope (this is important!)

4. Scope & Non-Scope

In scope: Exactly what we're building
Out of scope: What we're explicitly NOT building (and why)
Future considerations: Things we're deferring but designing for

5. User Flow

Walk through the happy path step-by-step:

User does X
System responds with Y
User sees Z

Then list edge cases and error states.

6. Technical Constraints

Platform/framework requirements
Performance requirements (latency, throughput)
Data requirements (storage, privacy, retention)
Integration points with existing systems

7. Open Questions

List anything unresolved. Don't hide uncertainty — surface it.

Prioritization Frameworks

RICE Score

Reach — How many users affected per quarter?
Impact — How much does it move the metric? (3=massive, 2=high, 1=medium, 0.5=low, 0.25=minimal)
Confidence — How sure are we? (100%, 80%, 50%)
Effort — Person-weeks to build

Score = (Reach x Impact x Confidence) / Effort

ICE Score (simpler)

Impact (1-10)
Confidence (1-10)
Ease (1-10)

Score = Impact x Confidence x Ease

Anti-Patterns to Avoid

Solution-first specs — Describing the UI before the problem
Unbounded scope — No "won't have" section
Metric-free specs — No way to measure success
Spec novels — 20-page docs nobody reads; keep it under 3 pages
Premature optimization — Specifying scale requirements for v0

Read the full file on GitHub · 77 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2d ago First seen · 77 lines · 72 tokens per session scan A 94d136835609

Subscribe to this mod's changes

specification is a skill published in the GitHub repository 0xranx/agentbrief (45 stars, last pushed 5mo ago), licensed MIT. It adds 72 tokens to every session and 674 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Documents Planning Writing and docs agent ai brief claude-code codex coding-agent

specification